Catheters with side ports are per se well known in the art. For instance, epidural catheters currently commercially available from Kendall Healthcare Company, a division of The Kendall Company, assignee of the present invention, include side holes or ports in order to provide better drug dispersion than that obtained from a single opening at the distal end of the catheter lumen. Such side ports are produced by mechanical methods, e.g. skiving with a sharp instrument or drilling with a small bit.
While entirely satisfactory for epidural catheters (or larger ones), the known mechanical procedures are not applicable for so-called microbore or small bore catheters, i.e. catheters no greater than 24 gauge (outer diameter=0.022 in). For example, the preferred microbore catheters contemplated by the present invention are almost two times smaller than the typical 20 gauge epidural catheter:
______________________________________ EPIDURAL MICROBORE SPINAL (20 gauge) (28 gauge) ______________________________________ OD 0.036 in OD 0.014 in ID 0.020 in ID 0.007 in ______________________________________ OD = outer diameter ID = inner diameter
By way of further explanation, the epidural catheter's side port diameter is typically on the order of 0.011 inch or on the order of fifty-five percent (55%) of the catheter's ID.
As is recognized in the art, the tendency for a patient to have rather severe headaches following spinal anesthesia is markedly reduced if a smaller needle is used. This in turn means that in conventional systems where the catheter is introduced through the needle, a smaller bore catheter is also required.
While for this reason microbore catheters are greatly preferred, if also desired that the microbore spinal catheter, like the larger epidural catheter have one or more side ports along with its distal end port to insure proper drug dispersion within the subarachnoid space. In the light of the state of the art at the time the present invention was made, these two characteristics appeared to be mutually exclusive so that one must either elect to have a microbore catheter without side ports or to have a larger bore catheter with side ports.
Stated simply, the task of the present invention was to devise a way to have the desired side port(s) in a microbore catheter.